(A) Field of the Invention
The present invention is related to an antenna apparatus and an antenna radome thereof and the related design method.
(B) Description of the Related Art
An antenna is essential for wireless communication systems, and affects signal quality of the entire system. The strength of a received signal is determined by the following equation:PL∝Pt·Gt·GL
where PL is receiving power at a receiving end, Pt is transmitting power at an emitting end, Gt is antenna gain of a transmitting antenna, and GL is antenna gain of a receiving antenna.
Accordingly, a design with an antenna of high gain (larger Gt or GL) will enhance signal quality of the wireless communication system (larger receiving power PL). Currently, a method for increasing antenna gain uses an antenna array in which the number of antenna elements is increased to improve the directionality, i.e., increasing the antenna gain. However, the above technique may incur problems of large loss of feeding signals and large volume of the entire antenna unit. Such tradeoffs would limit the increase of antenna gain, and large antennas are not suitable for small apparatuses.
In “Physical Review Letter” of November, 2002, Stefan Enoch disclosed an article titled “A Metamaterial for Directive Emission,” through which antenna gain can be increased significantly. A multi-layer square metal grid structure is positioned far from a dipole antenna, allowing the gain of the antenna to be increased to around 10 dB. However, the structure can only be disposed far from the dipole antenna, so its commercialization is not valuable.